The purpose of this study will be to: 1) compare the efficacy of lamivudine vs placebo in children with chronic hepatitis B with regard to a complete virologic response (loss of detectable HbeAg and HBV DNA from serum) and sustained normalization of serum alanine aminotransferase (ALT) levels at week 52; 2) compare the safety of lamivudine vs placebo in children with HBV infection.